Hydrosilylation reaction involving addition reaction of a Si—H functionality compound to a compound having a carbon-carbon double or triple bond is a useful means for synthesizing organosilicon compounds and is also industrially important synthetic reaction.
Pt, Pd and Rh compounds are known as catalysts for the hydrosilylation reaction. Most often used among them are Pt compounds as typified by Speier catalysts and Karstedt catalysts.
One of problems associated with Pt compound-catalyzed reactions is that the addition of a Si—H functionality compound to terminal olefin entails side reaction or internal rearrangement of olefin. Since this system does not display addition reactivity to internal olefin, unreacted olefin is left in the addition product. To complete the reaction, the olefin must be used previously in excess by taking into account the portion that is left behind due to side reaction.
Another problem is low selectivity between α- and β-adducts depending on the identity of olefin.
The most serious problem is that all Pt, Pd and Rh as the center metal are very expensive noble metal elements. Since metal compound catalysts which can be used at lower cost are desired, a number of research works have been made thereon. Among noble metals, Ru is available at relatively low cost. It would be desirable if Ru has a function to replace Pt, Pd, and Rh.
Patent Document 1 reports a Ru compound having a η6-arene group and organopolysiloxanes bonded or vinylsiloxanes coordinated to Ru as the center metal. It is shown that this compound is useful in addition reaction of methylhydrogenpolysiloxane and methylvinylpolysiloxane. Since the reaction at 120° C. leads to low yields, the reaction must be carried out at a high temperature of 160° C. to achieve high yields.
Many patent documents relating to Ru catalysts are cited in Patent Document 1 as reference (Patent Documents 2 to 6). From the aspects of reactivity, selectivity, and cost, it cannot be said that any Ru catalysts are superior to noble metal element based catalysts.
As for hydrogenation reaction of olefins, Non-Patent Document 1, for example, reports reaction using a trinuclear ruthenium catalyst, but further improvements are desired from the aspects of reaction temperature and yields.
One known method for reducing carbonyl compounds is by using hydrogen in the presence of aluminum hydride, boron hydride or noble metal catalysts. For ketones and aldehydes among carbonyl compounds, there are known hydride promoters and hydrogenation noble metal catalysts which allow progress of reaction under mild conditions and are stable and easy to handle. For reducing carboxylic acid derivatives such as esters and amides, the main method uses strong reducing agents such as lithium aluminum hydride and borane (Non-Patent Document 2). However, since these reducing agents are flammable, water-prohibitive substances, they are awkward to handle. Also careful operation is necessary when the aluminum or boron compound is removed from the desired compound at the end of reaction. In addition, high-temperature/high-pressure hydrogen is necessary for the reduction of carboxylic acid derivatives.
There are reported many methods using methylhydrogenpolysiloxane or hydrosilane compound which is stable in air and easy to handle, as the reducing agent. For this reaction, addition of strong acids or Lewis acids is necessary as well as expensive noble metal catalysts. One recent report relates to reductive reaction of carbonyl compounds in the presence of relatively low cost ruthenium catalysts. In some examples, the catalyst is applied to reductive reaction of amides which requires rigorous conditions in the prior art. While illustrative examples of the ruthenium catalyst are given in Non-Patent Documents 3 to 6, there is a desire to have high activity catalysts displaying a greater turnover count.